1. Field of the Invention
The present invention relates to a delivery warmer used for keeping cooked food warm and tasty during a delivery to a customer.
2. Prior Art
FIG. 11 shows an arrangement of a conventional delivery warmer. A container 101, made of cardboard or corrugated board, accommodates cooked food (not shown). A container casing 102 has a heat insulating structure according to which a heat insulating layer 103, such as a urethane foam layer, is fully provided along an entire surface of the container casing 102. The container 101 is accommodated in this container casing 102. A lid 104, provided at an opening end of the container casing 102, is closed to keep the cooked food warm and tasty in the container 101.
However, according to the above-described arrangement of the conventional delivery warmer, the temperature of the container casing 102 is substantially the same as an ambient temperature when the container 101 is accommodated in the container casing 102. There is a large temperature difference between the container casing 102 (e.g., room temperature) and the container 101 accommodating the cooked food (e.g., 50-100.degree. C.). Thus, the container 101, when entered in the container casing 102, is cooled down by the low-temperature body of the container casing 102.
Although the container casing 102 has the heat insulating structure, its ability is limited to a certain degree. Thus, the container casing 102 cannot stop releasing heat to the outside. Thus, the container casing 102 continuously radiates the heat to the outside, decreasing the temperature of the container 101. Therefore, there is a possibility that the cooked food cannot be kept warm and tasty after an elapse of a predetermined time which is normally required for delivering the container 101 to customers.